[Illustration: Fig. 11. Folder for Vertical Filing _Browne-Morse Co._] To preserve the idea of keeping all correspondence of one individual or firm together, folders are used. A folder, as shown in Fig. 11, consists of a piece of heavy manila paper folded, with one edge higher than the other, forming a pocket 9¾"×11⅞" in size. The higher or projecting edge of the folder is used for writing the name of the correspondent or other reference; or the folder may be made with a projecting tab for the purpose. One of these folders is used for each correspondent. Suppose, for example, that correspondence develops with Scott & Blake. The name of the concern is written on the projection of a folder, and all letters from, with copies of all letters written to, Scott & Blake are placed in this folder in the order of their date--the last letter in front. The folder provides a complete history of the correspondence with the concern. [Illustration: Fig. 12. Guides for Vertical Filing. _Browne-Morse Co._] The folders are filed on edge between guides or index cards having projections on which the indexes are written or printed. The indexes are fastened in a vertical file drawer, yet are removable. On the bottom of the guide, Fig. 12, is a square-cut projection, punched with a round hole. This projection drops into an opening in the bottom of the drawer, and engages a countersunk rod which is passed through the hole. The rod holds the guide firmly in place, but since the rod is removable, the guide can be taken out when it is desired to do so. The folders are not fastened in any way, and any folder can be removed without disturbing the others, as shown in Fig. 13. [Illustration: Fig. 13. Vertical File Drawer Showing Folders and Guides _Browne-Morse Co._] =Methods of Indexing.= There are four principal methods of indexing the vertical file; namely, the numerical, alphabetical, geographical, and subject. These four methods, with their resulting combinations, provide for the proper indexing of any class of papers. _Numerical Indexing._ Numerical indexing was the method first used with the vertical file, and still is extensively used. With the numerical system of indexing, the folders are numbered consecutively in the upper right-hand corner. The folders are filed in numerical sequence between guides, numbered usually by 10's, as shown in Fig. 14. Each correspondent is known by a number, and all of his correspondence--both original letters and copies of replies--is filed in a folder bearing his number. To locate his folder, a cross-index is necessary, as it is not possible to remember the numbers of all correspondents. The index is provided by a card on which is written the name, the folder number or file number, and any other memoranda that may be desired. The card is filed in a card drawer behind the proper alphabetical index guide, where it can be found very quickly. [Illustration: Fig. 14. Numerical Indexing _Browne-Morse Co._]